Some display devices displays the status of external apparatuses connected to programmable logic controllers (PLC). When an abnormality occurs in an external apparatus, such a display device has an alarm function of visually expressing an abnormality-occurring position on the external apparatus. An alarm-function setting apparatus, which provides various settings for the alarm function, creates, in accordance with an instruction from an operator, alarm-function information that is information set in the alarm function. The alarm-function information created by the alarm-function setting apparatus is transmitted from the alarm-function setting apparatus to the display device and used when the display device performs the alarm function.